For problem statement at 1000-1999/1800-1899/1800-1809/1800/problemB.txt this is a correct solution, but verifier at 1000-1999/1800-1899/1800-1809/1800/verifierB.go ends with All tests passed can you fix the verifier? ```go
package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	reader := bufio.NewReader(os.Stdin)
	writer := bufio.NewWriter(os.Stdout)
	defer writer.Flush()

	var t int
	fmt.Fscan(reader, &t)

	for i := 0; i < t; i++ {
		var n, k int
		fmt.Fscan(reader, &n, &k)
		var s string
		fmt.Fscan(reader, &s)

		lower := make([]int, 26)
		upper := make([]int, 26)

		for _, ch := range s {
			if ch >= 'a' && ch <= 'z' {
				lower[ch-'a']++
			} else {
				upper[ch-'A']++
			}
		}

		ans := 0
		extra := 0

		for j := 0; j < 26; j++ {
			cntL := lower[j]
			cntU := upper[j]

			if cntL < cntU {
				ans += cntL
			} else {
				ans += cntU
			}

			diff := cntL - cntU
			if diff < 0 {
				diff = -diff
			}

			extra += diff / 2
		}

		if k < extra {
			ans += k
		} else {
			ans += extra
		}

		fmt.Fprintln(writer, ans)
	}
}
```